1. Field of the Invention
The present invention relates generally to a tamper indicating closure for a container finish. More specifically, the invention relates to a closure having an annular skirt connected to a tamper indicating band which is provided with a plurality of tabs that extend inwardly and upwardly therefrom to engage a bead on a container finish. The invention further relates to a method for producing such a closure wherein the tabs are molded in the inwardly and upwardly extending position where they would interfere with demolding the closure.
2. Discussion of the Prior Art
A wide variety of closures have been invented for the container industry. Closures in common use today include roll-on closures which are usually formed from sheet aluminum and plastic closures with tamper indicating bands of the heat shrink type or the mechanical type. Each type of closure is adapted to coact with an annular bead provided around the finish of a container so that removal or attempted removal of a closure will cause an easily detected distortion of the closure indicative of its condition.
The present invention deals generally with closures having tamper indicating bands of the mechanical type. Such closures comprise an upper skirt portion with a band attached to it by a plurality of slender, frangible bridges. The tamper indicating band is provided with tabs adapted to engage an annular bead provided on a container finish during removal of the closure. As the closure is removed, movement of the tamper indicating band is prevented by the tabs which engage the annular bead on the container finish and cause substantial tensile stresses to be transmitted through the frangible bridges to the end that the frangible bridges fracture thereby separating the tamper indicating band from the closure to provide a positive visual indication of the removal or attempted removal.
Examples of closures with mechanical tamper indicating bands are disclosed in numerous patents including U.S. Pat. Nos. 4,546,892, 4,550,844, 4,196,818, 4,598,833, 4,595,110, 4,511,054, 4,506,795, 4,488,655, 4,478,343 and 4,572,388. In addition, International Patent Cooperation Treaty Application Publication No. WO 83/04402 discloses a closure with a tamper indicating band including tabs extending inwardly and upwardly to engage an annular bead on a container finish.
It is known that the manufacturer of closures with tamper indicating bands presents numerous problems. Some of these problems are discussed at length in U.S. Pat. No. 4,592,475. As is explained in this patent, one of the most difficult problems in molding closures having integral tamper indicating bands including upwardly and inwardly extending tabs is the extraction of the closure from a mold. According to this patent, it has been proposed to provide a separate, outer mold member that projects inwardly through the tamper indicating band to form, on each upwardly and inwardly extending tab, the surface which faces upwardly and outwardly. The patent disclosure goes on to point up the difficulties arising from the necessarily complex mold arrangement required to produce a closure in this manner. The patent goes on to disclose a complex mold with a three-piece core for producing, by injection molding, a closure with an integral tamper indicating band having tabs which extend upwardly and inwardly therefrom when the closure is removed from the mold. This contrasts with many prior art one-piece closures including tamper indicating bands having upwardly and inwardly extending tabs wherein the tabs are initially molded in a position where they do not extend upwardly and inwardly but wherein one or more additional operations are performed, subsequent to the molding of the closures, to permanently deflect the tabs so that they extend upwardly and inwardly from the tamper indicating band. These additional operations add to the manufacturing expense that is incurred in manufacturing such closures, especially closures of the self-sealing or linerless type which do not require a subsequent lining operation of a type that can also include a tab repositioning step. An example of a linerless type closure is illustrated in U.S. Pat. No. 3,255,909.